1. Field of the Invention
The present invention relates to a method for forming Ti--TiN laminates and a magnetron cathode suitable for continuously forming laminated layers of Ti (titanium) and TiN (titanium nitride) on the surface of a substrate.
2. Description of the Related Art
Conventionally, Ti--TiN laminates are used as ground barrier layers underlying aluminum films for wiring in semiconductor devices. With increases in the integration density of semiconductor devices, it has become necessary to improve the uniformity of the thicknesses of the Ti and TiN films. Additionally, there has been a problem of dust particles which are produced when TiN film adheres to an inner wall of the chamber and peels off in the TiN film formation process. These dust particles result in reductions in the yield of semiconductor devices.
Ti--TiN laminates are generally formed by first forming a Ti thin film by magnetron sputtering using a Ti target and then forming a TiN thin film by reactive magnetron sputtering by introducing a mixture of argon gas and nitrogen gas into the same chamber. However, a disadvantage of this process is that it is difficult to achieve good thickness distributions in both films when they are both formed in the same chamber with the same magnetron cathode.
Accordingly, the process for forming the Ti film and the process for forming the TiN film have been carried out in separate chambers having magnetron cathodes that can achieve good thickness distributions. In the Ti--TiN laminates formation process, it is suitable to use a multi-chamber system provided with a chamber for the Ti film formation process and a chamber for the TiN film formation process.
In order to form Ti--TiN laminates with the multi-chamber system, first a substrate is transferred into a first chamber for the Ti film formation process by a robot and a Ti film is formed by magnetron sputtering. After that, the substrate is transferred into a second chamber for the TiN film formation process and a TiN film is formed on the Ti film by reactive magnetron sputtering. However, fine dust particles, which are harmful to the devices being manufactured, increase as the formation process of the TiN film is continuously repeated in the chamber for the TiN film formation process. Through continuous repetition of the TiN film formation process, the TiN film deposited on the inner wall of the chamber becomes thicker and then peels off due to high internal stresses in the TiN film. The TiN which peels off the walls of the chamber becomes a source of particulate contamination.
One possible solution for preventing the dust particles from being produced is the technique of periodically coating the unwanted TiN film adhered to the inner wall of the chamber with a Ti film, for example one Ti coating per processing of 100 substrates, by Ti sputtering. Although this method allows fixing of the TiN film, with the Ti coating, it lowers the yield because the continuous production of Ti and TiN films is interrupted.